Quartus Quirk?

[Blackie Beard]

Hi;

I have a rom file for custom processor. I don't want to
use Quatus ROM Megafunctions because it's compiler
doesn't like intel hex files other that for byte-wide data,
and my data is 12 bits wide. So I wrote a custom utility
to create a ROM file (see at bottom of this post).
I know this may just be a Quartus quirk, but I want to
make sure it's not my verilog before I harass their techs.

My question is two-fold
1. Why does Quartus synthesize so that 800h word
ROM block uses A00h words? That is, I calculate that
worse case I should use 24,576 mem bits, yet Quartus
takes 30,720. If I prepend an "if(addr == 11'h7FF..."
and pull that out of the case statement, then it does
synthesize to the correct amount of memory. Why?
2. Is there simple way I'm overlooking to improve the
syntax or format or something to make the compiler
actually use only the memory bits that I actually use
(short of "if the address is within some range" stuff)?

Now here's the file in case anyone wants to test it:

module rom (
addr,
data
);
input [10:0] addr;
output [11:0] data;
reg [11:0] data;
always @(addr)
case (addr)
11'h000 : data = 12'h061;
11'h001 : data = 12'h004;
11'h002 : data = 12'hC07;
11'h003 : data = 12'h002;
11'h004 : data = 12'hC01;
11'h005 : data = 12'h021;
11'h006 : data = 12'hC17;
11'h007 : data = 12'h028;
11'h008 : data = 12'h201;
11'h009 : data = 12'h743;
11'h00a : data = 12'hA08;
11'h00b : data = 12'hC01;
11'h00c : data = 12'h021;
11'h00d : data = 12'h0E8;
11'h00e : data = 12'h743;
11'h00f : data = 12'hA08;
11'h010 : data = 12'h800;
11'h011 : data = 12'h064;
11'h012 : data = 12'hCFE;
11'h013 : data = 12'h006;
11'h014 : data = 12'hC30;
11'h015 : data = 12'h024;
11'h016 : data = 12'h580;
11'h017 : data = 12'h480;
11'h018 : data = 12'h720;
11'h019 : data = 12'hA18;
11'h01a : data = 12'h900;
11'h01b : data = 12'h5E0;
11'h01c : data = 12'h5A0;
11'h01d : data = 12'h4A0;
11'h01e : data = 12'h740;
11'h01f : data = 12'hA1E;
11'h020 : data = 12'h000;
11'h021 : data = 12'h000;
11'h022 : data = 12'h5C0;
11'h023 : data = 12'h600;
11'h024 : data = 12'hA23;
11'h025 : data = 12'h506;
11'h026 : data = 12'hA26;
11'h7FF : data = 12'h45C;
default : data = 12'h000;
endcase
endmodule

Thanks much!
BB

 

[Petter Gustad]

"Blackie Beard" <bb@fearlessimmortalwretch.com> writes:

Hi;

I have a rom file for custom processor. I don't want to
use Quatus ROM Megafunctions because it's compiler
doesn't like intel hex files other that for byte-wide data,

Quartus is using mif files. They are very verbose and self
explanatory. Take a look in your Quartus installation if you have any
sample mif files. The nios-convert program can convert from/to mif,
dat (for $readmem) or srec. Converting hex to mif is probably a lot
simpler than hex to verilog.

Are you sure that Quartus is generating a ROM and not logic from your
case statement?

If you do get a ROM it will allocate a hardmacro ROM. They have fixed
sizes and are depending upon your target architecture, e.g. Cyclone
have 4608 bit RAM/ROMs.

Petter

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

 

[Blackie Beard]

"Petter Gustad" <newsmailcomp5@gustad.com> wrote in message
news:m3d61nbiai.fsf@scimul.dolphinics.no...

"Blackie Beard" <bb@fearlessimmortalwretch.com> writes:

Hi;

I have a rom file for custom processor. I don't want to
use Quatus ROM Megafunctions because it's compiler
doesn't like intel hex files other that for byte-wide data,

Quartus is using mif files. They are very verbose and self
explanatory. Take a look in your Quartus installation if you have any
sample mif files. The nios-convert program can convert from/to mif,
dat (for $readmem) or srec. Converting hex to mif is probably a lot
simpler than hex to verilog.

Are you sure that Quartus is generating a ROM and not logic from your
case statement?

If you do get a ROM it will allocate a hardmacro ROM. They have fixed
sizes and are depending upon your target architecture, e.g. Cyclone
have 4608 bit RAM/ROMs.

Petter

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

No - that is, Quartus is not generating logic from that file. The
reading of how much memory it took was from the tree control
showing logic elements and memory bits.

Maybe you can compile it? Just that file should compile.

Thx,
BB